Canadian Arctic Islands Research Articles

The role of seasonal migration in the near-total loss of caribou on south-central Canadian Arctic Islands

The role of seasonal migration in the near-total loss of caribou on south-central Canadian Arctic Islands

Biomarker determination as a provenance tool for detrital carbonate events (Heinrich events?): Fingerprinting Quaternary glacial sources into Baffin Bay

Sedimentary deposits associated with Heinrich events are anomalously rich in detrital carbonate. Off Hudson Strait the dominant carbonate is calcite whereas at distal sites in the North Atlantic dolomite is dominant (more diagnostic?). A significant source for dolomite is its outcrop at the northern end of Baffin Bay where major ice streams from the Laurentide, Innuitian and Greenland ice sheets converged. The provenance of samples containing detrital carbonate, mainly dolomite, from a core in Baffin Bay has been confirmed using organic geochemistry to distinguish between alternative sources, based upon the thermal maturity of organic matter in carbonates of the source region. The core contained five distinct carbonate units dating between ∼ 14 and 51 cal ka BP and indicates significant ice stream instability associated with iceberg calving and significant volumes of meltwater. The exact temporal relationship to Heinrich events is not yet clear. A long mid-Wisconsin interval (∼ 38 to 22 cal ka BP) devoid of detrital carbonate suggests a major reduction in ice extent at high northern latitudes. The core samples yield thermally sensitive biomarker ratios comparable to those from Laurentian carbonates in the Canadian Arctic islands but unlike those from North Greenland, identifying the former region as their provenance. However, a Late Holocene sample from off Newfoundland shows a stronger affinity with Greenland.

CO2 isotopes as tracers of firn air diffusion and age in an Arctic ice cap with summer melting, Devon Island, Canada

Firn air and ice have been sampled and analyzed for trace gases (CO2, N2O, CH4, and CO) and isotopes (14C, 13C, and 18O of CO2; 3H of ice) at 3 m intervals from the surface to the depth of closure at 60 m on the Devon Island Ice Cap, a low‐elevation permanent glacier in the Canadian Arctic Islands, to investigate firn diffusion and the effects of summer melting. The 14CO2 profile from the permeable firn includes the 1963 thermonuclear peak at a depth of 53.9 ± 1.5 m. The twofold increase and rapid decay that characterize the recent atmospheric history for 14CO2 provide a robust atmospheric scenario that is used with a firn air diffusion model to inversely construct the firn diffusivity profile. The results show a permeable but essentially nondiffusive zone from 50 to 60 m depth. A firn‐ice age profile was produced from density measurements, and accumulation rates were calibrated with the depth of the 1963 thermonuclear 3H peak. The average ages for CO2 in the sampled firn air profile were determined by a new method based on the rate of 18O exchange between CO2 and the ice matrix. Calibrated with the 1963 peak for thermonuclear 14CO2, a 21.2‐year reaction halftime is calculated for exchange taking place at the firn temperature of −22.8°C on Devon. This gives an average age of 54.9 (+6.0/−12.0) years for firn air at 60 m depth in 140‐year‐old ice. Thus CO2 has a mean age 85 years younger than associated ice at the point of occlusion. The measured in firn air provides no indication of alteration by summer melting, which is attributed to a high degree of convective and diffusive flushing of the upper firn as shown by diffusion modeling. This suggests that ice sheets with summer melt layers can reliably preserve atmospheric trace gas signals.

A northwest North American training set: distribution of freshwater midges in relation to air temperature and lake depth

Freshwater midges, consisting of Chiro- nomidae, Chaoboridae and Ceratopogonidae, were assessed as a biological proxy for palaeoclimate in eastern Beringia. The northwest North American training set consists of midge assemblages and data for 17 environmental variables collected from 145 lakes in Alaska, British Columbia, Yukon, Northwest Territories, and the Canadian Arctic Islands. Canon- ical correspondence analyses (CCA) revealed that mean July air temperature, lake depth, arctic tundra vegetation, alpine tundra vegetation, pH, dissolved organic carbon, lichen woodland vegetation and sur- face area contributed significantly to explaining midge distribution. Weighted averaging partial least squares (WA-PLS) was used to develop midge inference models for mean July air temperature (rboot = 0.818, RMSEP = 1.46� C), and transformed depth (ln (x+1); rboot = 0.38, and RMSEP = 0.58).

On the Meteorological Instruments and Observations Made during the 19th Century Exploration of the Canadian Northwest Passage

Meteorological records from about 30 British Navy ships that overwintered in the Canadian Arctic islands between 1818 and 1859 are the earliest detailed baseline of direct historical data in this region against which modern and future climate trends can be assessed. We describe the types of meteorological instruments and the observational methods employed aboard these ships. For measuring air temperatures, both mercurial and spirit thermometers were used. Observations of atmospheric pressure were made using marine and aneroid barometers. Wind direction and speed were also logged. The Royal Navy’s ordered and disciplined daily regime was well-suited to regular scientific observations. Individual instruments on most Navy ships were calibrated against established Royal Observatory standards before and after expeditions. Many recording officers commented on the relative unreliability of spirit thermometers below the freezing point of mercury. Little contemporary written evidence exists regarding absolute accuracy or precision of meteorological instruments taken to the Arctic, but some calibration data are available to assess typical instrument errors between 32° and −38°F (0° and −39°C). Our comparison of minimum daily temperatures from four overwintering ships in 1853 and 1854 shows very high correlation coefficients. The mutual consistency of these records implies good instrumental precision. Although the absolute accuracy of temperatures recorded below the freezing point of mercury is in doubt, those above this point are relatively accurate. Guidance on the preferred methods of observing and recording were codified in, for example, the Admiralty’s Manual of Scientific Enquiry (Herschel, 1851). Meteorological registers were regarded as official documents that were, as far as possible, required to be complete and no attempt was to be made to fill in missing data. The need to screen or cover instruments from both solar and terrestrial radiation was also recognized from the earliest expeditions. It was not until the 1850s that standardizing the exposure of thermometers was resolved through the introduction of louvered screens. This unique set of ships’ meteorological registers presents opportunities to investigate a variety of meteorological parameters for the Canadian High Arctic in the 19th century, allowing quantitative assessment of change relative to contemporary climate.

The paradox of the global standard Late Ordovician–Early Silurian sea level curve: Evidence from conodont community analysis from both Canadian Arctic and Appalachian margins

Relative sea level fluctuations in the Late Ordovician–Early Silurian were largely driven by Gondwana deglaciation, three possible short-lived ice readvances, and the closure of the Iapetus Ocean. This study establishes and compares sea level events on the Canadian Arctic and Appalachian margins of Laurentia based on the pattern of conodont communities, and demonstrates that sea level events were not synchronous on the two margins. Conodont data were compared for a) the Arctic margin from the Cape Phillips Formation (Richmondian, Upper Ordovician through lower Sheinwoodian, Lower Silurian), Cornwallis Island, Canadian Arctic Islands, and b) the Appalachian margin from the upper Ellis Bay, Becscie, Merrimack, Gun River, Jupiter and Chicotte formations (Richmondian, Upper Ordovician, Rhuddanian, Aeronian, and most of Telychian, Lower Silurian), Anticosti Island, Quebec. The pattern of Late Ordovician–Early Silurian conodont communities is established based on three cluster analyses on conodonts from Cornwallis Island (4967 specimens representing 54 species from 77 samples, Cape Phillips Formation) and Anticosti Island (1980 specimens representing 21 species from 25 samples, upper Ellis Bay Formation; 24,839 specimens representing 42 species from 123 samples, Becscie, Merrimack, Gun River, Jupiter and Chicotte formations). Overall, the sea level curves inferred from the distribution of the conodont communities from Cornwallis and Anticosti exhibit gradual and rapid oscillating patterns, respectively. Specifically, during the time interval of the latest Ordovician and the Early Silurian (Rhuddanian), the sea level behaved differently in these two regions: 1) during the latest Ordovician, conodont community changes show the different patterns in the two regions, which reflects a transgression on Cornwallis, but a regression on Anticosti; 2) during the earliest Rhuddanian, similar conodont communities arose in both regions, but they indicate a regression on Cornwallis and a transgression on Anticosti; 3) in the early Rhuddanian, these communities were replaced by a deeper water community on Cornwallis and a shallower water community on Anticosti, which suggest a transgression on Cornwallis and a regression on Anticosti; 4) a highstand drove out almost all conodonts from Anticosti by the end of Rhuddanian, which is not seen on Cornwallis; 5) a deep-water conodont community remained almost unchanged on Cornwallis from the late Rhuddanian to the early Aeronian, whereas a shallow water conodont community returned to Anticosti in the early Aeronian. However, the sea level dropped on both Cornwallis and Anticosti during the late Telychian, and the sea level curves show a similar pattern. The difference in the sea level pattern during the late Richmondian, Rhuddanian and Aeronian on both the northern and southern margins of Laurentia reflected by conodont communities is supported by the studies on Quaternary glaciation/deglaciation events, where the melting of an ice sheet was accompanied by sea level change but with variable regional isostatic effects that do not generate a uniform global eustatic signal.

Carbon isotope chemostratigraphy in Arctic Canada: Sea-level forcing of carbonate platform weathering and implications for Hirnantian global correlation

Three sections through latest Ordovician strata in the Canadian Arctic Islands have been studied for carbon isotopes, derived from the organic matter (δ 13C org) and whole-rock carbonate (δ 13C carb) fractions. The sections are well constrained biostratigraphically using graptolites, lithostratigraphically and palaeogeographically. δ 13C org data appear to provide a signal that mainly reflects chemical changes in the seawater, whereas the δ 13C carb data seem to have been variably affected by sediment reworking and diagenesis. Results show that a positive δ 13C org excursion of 3–6‰ begins just below the base of the Hirnantian Stage and peaks in the lower part of the Normalograptus extraordinarius biozone of lower Hirnantian. This is followed by an interval of reduced δ 13C values and a second peak of similar magnitude, which occurs in the lower Normalograptus persculptus biozone (upper Hirnantian). These peaks appear to correlate well with episodes of glacial expansion described from West Africa. Global correlation between δ 13C curves suggests that the timing of peak positive excursions is not completely synchronous between different regions. In particular, the lower Hirnantian peak seen in Arctic Canada and some other areas appears to be suppressed in sedimentary successions from the circum-Iapetus region, where peak values occur in later Hirnantian time. Thus, no single, regional δ 13C curve can reliably serve as a benchmark for high-resolution, global correlation. These data provide support for the hypothesis that the positive δ 13C shifts seen in these sections and many others worldwide are the result of increased rates of weathering of carbonate platforms that were exposed during the glacio-eustatically controlled sea-level fall. This caused the isotope value of the C-weathering flux to shift towards the 13C-enriched carbonate end-member, increasing the δ 13C value of carbon transported by rivers to both epeiric seas and the oceans. Magnitude differences between Hirnantian δ 13C excursions in shallower and deeper water parts of epeiric sea basins, as well as between different regions, may be explained by water mass differentiation between those regions. The positive shift in the δ 13C value of the Hirnantian oceans is predicted to be about 2–3‰, which is about half the value of the larger excursions found in basin proximal settings of low latitude epeiric seas.

Distribution of Chironomidae (Insecta: Diptera) Head Capsules in Recent Sediments of Canadian Arctic Lakes

Thirty-two taxa of chironomid larvae were collected from the sediments of 50 lakes from across the Canadian Arctic Islands. Most chironomid taxa living in the Arctic have wide distributions, with only one taxon, Abiskomyia, showing a clear geographic limitation in this region. Many of these taxa have habitat preferences, among which lake morphometry, pH, nutrients and temperature are important. Due to the complex environmental patterns in the Arctic, lakes in both the northern and southern portion of the Canadian Arctic Archipelago have warmer temperatures and the chironomid assemblages of these two regions resemble each other more than those of the intervening central islands. Chironomid diversity is lowest in the central arctic islands, primarily Devon and Cornwallis Island, where the combination of low nutrients and cold temperatures provide the most severe environment for chironomid survival.

Sequence stratigraphy and evolution of Middle to Upper Devonian Beaverhill Lake strata, south-central Alberta

Abstract Beaverhill Lake strata of late Givetian to early Frasnian age in the subsurface of south-central Alberta consist of shelfal limestones, dolostones and some anhydrites as well as basinal limestones and shales, and range in thickness from 75 to 240 m. These strata were deposited in the Central Alberta Basin and on banks (platforms) or isolated reefs on both sides of the basin. An integrated physical stratigraphic/sedimentological and conodont biostratigraphic study of these strata reveals that Beaverhill Lake strata form most of one overall (first-order) transgressive-regressive (T-R) cycle of sedimentation that also includes coastal plain and marginal marine deposits of the underlying Watt Mountain Formation (conodont zone of Lower subterminus Fauna) and shallow-marine carbonates of the lower part of the overlying Cooking Lake Formation on the east side of the Central Alberta Basin and the lower part of the overlying Leduc Formation on the west side of the basin. This overall T-R cycle consists of two major (second-order) T-R cycles. The lower, second-order cycle extends from the sub-Watt Mountain subaerial unconformity up to a widespread subaerial unconformity (R4 or Upper C) on banks and isolated reefs on both the east and west sides of the Central Alberta Basin and its equivalent, conformable transgressive surface in the basinal succession and includes Beaverhill Lake strata deposited during conodont zone of Upper subterminus Fauna to upper MN2 Zone. The upper, second-order T-R cycle extends from this subaerial unconformity or its basinal equivalent up to the conformable transgressive surface at the top of the Waterways Formation in the Central Alberta Basin or up to an equivalent position in the lower part of the Cooking Lake and Leduc formations on both sides of the basin. Strata in the upper, second-order cycle were deposited from the upper MN2 to MN4 conodont zones. The Beaverhill Lake portion of each of these second-order cycles includes seven third-order sequences, the basic stratigraphic unit of this study. T-R cycles were produced by the interaction of base-level changes, extrabasinal tectonism and depositional controls. The interaction of these controls resulted in different stacking styles of growth on banks and isolated reefs on the east and west sides of the Central Alberta Basin. Areally widespread progradation of carbonate banks on the east side of the basin was directly related to the delivery of argillaceous sediment to the basin from the northeast. The most likely terrigenous source areas were an uplifted portion of the Caledonian orogenic belt, exposed along the east coast of Greenland, or the eastern part of the Franklinian orogenic belt, exposed in the Canadian Arctic islands. The deposition of basinal argillaceous strata in the study area was episodic. The onset of episodes of argillaceous sediment deposition corresponds to transgressive facies shifts and was triggered by increased rates of base-level rise and not to shelfal incision and sediment bypass during intervals of base-level fall. Clay-rich sediment was carried by either surface, or near-surface, marine currents, or by episodic storm-generated currents or episodic storm-generated sediment-gravity flows. The southwesterly transport of this sediment was due to the southeasterly paleo-trade winds or to storm tracks that moved parallel to these winds. During some intervals, this fine terrigenous sediment appreciably infilled portions of the basin proximal to coeval carbonate banks on the east side of the basin. Westerly, leeside shedding of lime mud from these carbonate banks by storm-induced currents resulted in even further infilling of the basin. As a result, these portions of the basin became sufficiently infilled to promote the westerly, leeside bank progradation during intervals of either slower base-level rise or base-level fall. Banks and most isolated reefs on the west side of the Central Alberta Basin were far removed from the entry of clay-rich sediment into the basin. Therefore, portions of the Central Alberta Basin proximal to these banks and isolated reefs were not significantly infilled by coeval argillaceous successions. Lacking appreciable argillaceous sediment infill of these portions of the basin, banks and most isolated reefs on the west side of the Central Alberta Basin prograded basinward only by building out over their own debris and finer bank- or reef-derived sediment. This severely limited the extent of bank or isolated reef progradation. As a consequence, banks and isolated reefs on the west side of the Central Alberta Basin display an overall retreating or backstepping style of growth. The major episodes of isolated reef growth occur at different times on the east and west sides of the Central Alberta Basin and reflect the difference in the prior evolution of carbonate banks in both areas. Trends, inherent in both stratigraphic cross-sections and in cumulative isopach maps, also suggest that most of the micrite in basinal limestones was shed from upslope portions of carbonate ramps, from areas to the northeast of the sub-Cretaceous subcrop unconformity.

Limnology of 46 lakes and ponds on Banks Island, N.W.T., Canadian Arctic Archipelago

The goal of this study was to describe and quantify the physical and chemical limnological properties of 46 lakes and ponds on Banks Island, to explore the effects of ecoclimatic differences on the water chemistry of these study sites, and to establish baseline conditions for this previously unexplored limnological region, which could then be used in subsequent long-term environmental monitoring programs. A key finding was that the study sites on Banks Island represented a large nutrient concentration gradient from ultra-oligotrophic to hypereutrophic waters. In general, the study sites were relatively nutrient rich by Arctic standards (i.e. mean total nitrogen (TNmean)=504.2μg/l and mean total phosphorus (TPUmean)=18.0μg/l); concentrations that are amongst the highest of any previous limnological survey from similar latitudes. Dissolved organic carbon (DOC) concentrations were also some of the highest reported to date amongst all other Canadian Arctic island limnological surveys. These values reflect the milder climate, concentrated animal life and lushness of Banks Island, as compared to other Canadian Arctic Archipelago islands. Principal components analysis (PCA) separated sites along a conductivity/ionic and elevation gradient on Axis 1 (λ1=0.343), and a metal (Fe, Zn, Al) and alkalinity-related (DIC, pH) gradient on the second axis (λ2=0.187). Canonical variate analysis (CVA) was used to explore the classification of the study sites into Low Arctic, Mid Arctic or High Arctic designations based on their limnological characteristics.

A probable late Neoproterozoic age for the Kennedy Channel and Ella Bay formations, northeastern Ellesmere Island and its implications for passive margin history of the Canadian Arctic

The Kennedy Channel and Ella Bay formations are the two oldest stratigraphic units exposed in the Franklinian margin sedimentary sequence in the Canadian Arctic Islands. An Early Cambrian age had previously been accepted by the occurrence of trilobites and small shelly fossils in the type section of the Kennedy Channel Formation. Reinvestigation of the area around the type section shows that several large strike-slip faults cut the succession and that the olenelloid trilobites are from an infaulted slice of a younger unit, the Lower Cambrian Kane Basin Formation. Thus, there is no unambiguous paleontological evidence for the age of either the Kennedy Channel or Ella Bay formations. However, the abundance of stromatolites, absence of trace fossils, and separation from overlying Lower Cambrian clastics by a regional angular unconformity indicate a probable late Neoproterozoic age for these two formations. The Ella Bay Formation likely correlates with the Portfjeld Formation in North Greenland, the Spiral Creek Formation in East Greenland, and the Risky Formation of the Mackenzie Mountains in northwestern Canada. The passive margin that existed in northern Laurentia during the early Paleozoic was, therefore, established in the late Neoproterozoic, and the onset of rifting must have preceded this, rather than occurring in the Early Cambrian as some authors have suggested.

A Systematic Analysis of the Alpine Saxifrage Complex (Saxifragaceae) in the Canadian Arctic Islands Using Morphology and Chloroplast DNA Data

The Saxifraga nivalis complex displays significant ecological, morphological and cytological variation. Most European studies suggest that the S. nivalis complex comprises two distinct species: Saxifraga nivalis sensu stricto and Saxifraga tenuis. However, the presence of intermediate morphotypes, inconsistencies in chromosomal counts and variability in morphological keys and descriptions have led to different taxonomic interpretations of the complex in North America. This study investigated the systematics of Canadian Arctic Island members of this complex from 157 specimens using 23 morphological characters. Principal component analysis of the morphological data revealed two adjacent clusters, corresponding to the two taxa and consistent with a close morphological similarity and the presence of hybrids. A preliminary restriction site analysis of five non-coding regions of the chloroplast genome, trnH-trnK, trnT-trnF, trnF-trnV, trnV-rbcL and rbcL-ORF106, was conducted using 21 restriction endonucleases. This analysis indicated a length difference between the trnT-trnF region of S. nivalis and that of S. tenuis, but no difference in restriction sites for any of the assayed regions. These results confirm that in the Canadian Arctic, the S. nivalis complex consists of two closely related, largely sympatric species, with notable morphological variability, and possible hybrids.

Sedimentary Cover of the Canadian Shield through Mesozoic Time Reflected by Nd Isotopic and Geochemical Results for the Sverdrup Basin, Arctic Canada

Abstract The Sverdrup Basin of the Canadian Arctic Islands contains a sedimentary record, with only short breaks, from Early Carboniferous to Late Cretaceous time and can be used to document the nature of sediments delivered from northern Canada and Greenland. Sm‐Nd isotopic analysis of 72 sedimentary rock samples from the Sverdrup Basin, coupled with trace element characterization, shows that for most of Carboniferous to Late Cretaceous time, the sediment supply in the northern part of North America was dominated by a single broad provenance; 56 of the 72 samples lie squarely within the Nd isotopic evolution of a clastic sedimentary cover delivered to the region following 450–350 Ma Caledonian and Franklinian mountain building in Greenland and the Canadian Arctic Islands. Cratonic Shield sources in Greenland and Canada are hardly evident in the record, and significant contributions to the sediment budget from any source other than the post‐mid‐Paleozoic orogenic cover occurred only during four relatively...

Eurekan transpressive deformation in the Wandel Hav Mobile Belt (northeast Greenland)

Besides the ∼W‐E trending Kap Cannon Thrust Zone and Harder Fjord Fault Zone, the 300 km long and NW‐SE striking Wandel Hav Mobile Belt represents the third major fault zone in north Greenland. Structural analyses in several areas of this belt suggest that compressive deformation is characterized by transpressive dextral strike‐slip kinematics. This is demonstrated by a combination of folding around ∼W‐E axes, approximately north and south directed reverse faulting, and dextral strike‐slip displacements along NW‐SE trending fault lines. The initial formation of the long, linear faults is interpreted to be related to deformational events in Late Paleozoic, Triassic‐Jurassic, and Late Cretaceous times. Due to the lack of structural evidence, we assume that deformations led to the generation of extension faults which probably were reactivated during dextral strike‐slip tectonism. It is suggested that dextral transpressive deformation was coeval with ∼N‐S compression at the Harder Fjord Fault Zone and Cap Cannon Thrust Zone and took place during Eocene (Eurekan) times. Dextral strike‐slip tectonism in the Wandel Hav Mobile Belt was the result of ∼N‐S compression due to a general northward movement of the Greenland plate. As a zone of crustal weakness, the belt can be interpreted as the onshore equivalent of the main transcurrent fault zone (De Geer Fault) which caused the intracontinental dextral slip of Svalbard (Barents Shelf) relative to north Greenland during Early Tertiary (Eurekan) times and prior to their separation. In this configuration, it represents one part of the belt of Eurekan deformation which extends from the Canadian Arctic islands over north Greenland to the Barents Shelf where compressive deformation is recorded in the West Spitsbergen Fold‐and‐Thrust Belt.

Status, population fluctuations and ecological relationships of Peary caribou on the Queen Elizabeth Islands: Implications for their survival

The Peary caribou (Rangifer tarandus pearyi) was recognized as 'Threatened' by the Committee on the Status of Endangered Wildlife in Canada in 1979 and 'Endangered' in 1991. It is the only member of the deer family (Cervidae) found on the Queen Elizabeth Islands (QEI) of the Canadian High Arctic. The Peary caribou is a significant part of the region's biodiversity and a socially important and economically valuable part of Arctic Canada's natural heritage. Recent microsatellite DNA findings indicate that Peary caribou on the QEI are distinct from caribou on the other Arctic Islands beyond the QEI, including Banks Island. This fact must be kept in mind if any translocation of caribou to the QEI is proposed. The subspecies is too gross a level at which to recognize the considerable diversity that exists between Peary caribou on the QEI and divergent caribou on other Canadian Arctic Islands. The Committee on the Status of Endangered Wildlife in Canada should take this considerable diversity among these caribou at below the subspecies classification to mind when assigning conservation divisions (units) to caribou on the Canadian Arctic Islands. In summer 1961, the first and only nearly range-wide aerial survey of Peary caribou yielded a population estimate on the QEI of 25 845, including about 20% calves. There was a strong preference for range on the western QEI (WEQI), where 94% (24 363) of the estimated caribou occurred on only 24% (ca. 97 000 km2) of the collective island-landmass. By summer 1973, the overall number of Peary caribou on the QEI had decreased markedly and was estimated at about 7000 animals. The following winter and spring (1973-74), the Peary caribou population declined 49% on the WQEI. The estimated number dropping to <3000, with no calves seen by us in summer 1974. Based on estimates from several aerial surveys conducted on the WQEI from 1985 to 1987, the number of Peary caribou on the QEI as a whole was judged to be 3300-3600 or only about 13-14% of the 1961 estimate. After a partial recovery in the late 1980s and early 1990s, Peary caribou on the WQEI declined drastically between 1994 and 1997 and were estimated at an all-time known low of about 1100 animals by summer 1997. The number of Peary caribou on the QEI in summer 1997 was likely no more than 2000-2400 or only 8-9% of the 1961 estimate. The four known major die-offs of Peary caribou on the WQEI between 1973 and 1997 occurred during winter and spring periods (1 Sep-21 Jun) with significantly greater (P<0.005) total snowfall, when compared to the long-term mean obtained from 55 caribou-years (1 Jul-30 Jun), 1947/48-2001/02, of weather records from Resolute Airport on Cornwallis Island. Of ecological significance is that the die-offs occurred when the caribou were at low mean overall densities and involved similar high annual rates of loss among muskoxen (Ovibos moschatus). All of the available evidence indicates that Peary caribou (and muskoxen) on the QEI experienced die-offs from prolonged, under-nutrition (starvation) caused by relative unavailability of forage-the forage was there but it was inaccessible to the caribou due to snow and/or ice cover. We cannot control the severe weather that greatly restricts the forage supply but we should try to reduce the losses of Peary caribou from other sources-humans, predators and competitors.

Study of the natural gas hydrate trap zone and the methane hydrate potential in the Sverdrup Basin, Canada

The methane hydrate stability zone beneath Sverdrup Basin has developed to a depth of 2 km underneath the Canadian Arctic Islands and 1 km below sea level under the deepest part of the inter-island sea channels. It is not, however, a continuous zone. Methane hydrates are detected in this zone, but the gas hydrate/free gas contact occurs rarely. Interpretation of well logs indicate that methane hydrate occurs within the methane stability zone in 57 of 150 analyzed wells. Fourteen wells show the methane hydrate/free gas contact. Analysis of the distribution of methane hydrate and hydrate/gas contact occurrences with respect to the present methane hydrate stability zone indicate that, in most instances, the detected methane hydrate occurs well above the base of methane hydrate stability. This relationship suggests that these methane hydrates were formed in shallower strata than expected with respect to the present hydrate stability zone from methane gases which migrated upward into hydrate trap zones. Presently, only a small proportion of gas hydrate occurrences occur in close proximity to the base of predicted methane hydrate stability. The association of the majority of detected hydrates with deeply buried hydrocarbon discoveries, mostly conventional natural gas accumulations, or mapped seismic closures, some of which are dry, located in structures in western and central Sverdrup Basin, indicate the concurring relationship of hydrate occurrence with areas of high heat flow. Either present-day or paleo-high heat flows are relevant. Twenty-three hydrate occurrences coincide directly with underlying conventional hydrocarbon accumulations. Other gas hydrate occurrences are associated with structures filled with water with evidence of precursor hydrocarbons that were lost because of upward leakage.

A re-evaluation of species limits in Canadian Arctic Island Puccinellia (Poaceae): resolving key characters

This study examined morphological variation for species of Puccinellia that have traditionally posed problems of identification in the Canadian Arctic Archipelago. The first part of the study involved a re-examination of several characters that were difficult to define or describe. Microscopic examination of lemma and glume apices revealed that the characters "erose-ciliolate" lemma and glume apex margins are more accurately divided into two characters: degree to which they are erose, and presence of trichomes. These trichomes consist of acute or acuminate cells that protrude 15–35 µm from the margin, sometimes with a spinulose tip up to 10 µm long. The term "thickened pedicel" is clarified to mean thickened below the apex in relation to the apex. The second part of the study involved preliminary morphometric analyses on the above-mentioned revised characters, plus other characters previously shown to have low plasticity in this genus, for 10 recognized species that are difficult to distinguish. Many species or species complexes resolved to a small degree, but no taxa formed distinct groups. Correlations among many characters were low, accounting for a low percentage of variation explained by the first few principal components. Hypotheses of species boundaries and a preliminary revised key to species and species groups, incorporating findings from this study, are presented.Key words: Puccinellia, Canadian Arctic, morphology, trichomes, principal components analysis, cluster analysis.

A re-evaluation of species limits in Canadian Arctic Island <i>Puccinellia</i> (Poaceae): resolving key characters

A re-evaluation of species limits in Canadian Arctic Island <i>Puccinellia</i> (Poaceae): resolving key characters

Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

Abstract The composition and distribution of ice-rafted glacial erratics in late Quaternary sediments define the major current systems of the Arctic Ocean and identify two distinct continental sources for the erratics. In the southern Amerasia basin up to 70% of the erratics are dolostones and limestones (the Amerasia suite) that originated in the carbonate-rich Paleozoic terranes of the Canadian Arctic Islands. These clasts reached the Arctic Ocean in glaciers and were ice-rafted to the core sites in the clockwise Beaufort Gyre. The concentration of erratics decreases northward by 98% along the trend of the gyre from southeastern Canada basin to Makarov basin. The concentration of erratics then triples across the Makarov basin flank of Lomonosov Ridge and siltstone, sandstone and siliceous clasts become dominant in cores from the ridge and the Eurasia basin (the Eurasia suite). The bedrock source for the siltstone and sandstone clasts is uncertain, but bedrock distribution and the distribution of glaciation in northern Eurasia suggest the Taymyr Peninsula-Kara Sea regions. The pattern of clast distribution in the Arctic Ocean sediments and the sharp northward decrease in concentration of clasts of Canadian Arctic Island provenance in the Amerasia basin support the conclusion that the modern circulation pattern of the Arctic Ocean, with the Beaufort Gyre dominant in the Amerasia basin and the Transpolar drift dominant in the Eurasia basin, has controlled both sea-ice and glacial iceberg drift in the Arctic Ocean during interglacial intervals since at least the late Pleistocene. The abruptness of the change in both clast composition and concentration on the Makarov basin flank of Lomonosov Ridge also suggests that the boundary between the Beaufort Gyre and the Transpolar Drift has been relatively stable during interglacials since that time. Because the Beaufort Gyre is wind-driven our data, in conjunction with the westerly directed orientation of sand dunes that formed during the last glacial maximum on the North Slope of Alaska, suggests that atmospheric circulation in the western Arctic during late Quaternary was similar to that of the present.

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

Late Ordovician to earliest Silurian is an important geological period marked by large geological and biological events. However, the strata and fossils of this interval are not complete in many parts of the world. Based on studies of 43 sites in South China, in particular the continuous sections on the Yangtze platform, we recognize a complete succession including seven graptolite zones and two shelly faunas. In ascending order, the graptolite zones are the Dicellograptus complanatus, Dicellograptus complexus, Paraorthograptus pacificus (including Lower Subzone, Tangyagraptus typicus Subzone and Diceratograptus mirus Subzone), Normalograptus extraordinarius–Normalograptus ojsuensis, Normalograptus persculptus, Akidograptus ascensus and Parakidograptus acuminatus zones. The shelly faunas are the Foliomena–Nankinolithus and Hirnantia faunas, which may be correlated with D. complanatus Zone and N. extraordinarius–N. ojsuensis to part of N. persculptus zones respectively. The biozonation through this interval from the Yangtze region can be correlated with that of other parts of the world such as Dob's Linn in Scotland, Spain and Portugal, Thuringia–Saxonia–Bavaria, Bohemia, Poland, Kazakhstan, Kolyma, Malaya Peninsula, Yukon, Canadian Arctic Islands, Nevada, Argentina, Niger and Victoria, Australia. The Hirnantian Substage, which has been proposed by us recently, includes the N. extraordinarius–N. ojsuensis Zone, Hirnantia fauna and N. persculptus Zone. The base of the Hirnantian Substage is marked by the First Appearance Data (FADs) of N. extraordinarius and N. ojsuensis, which have been determined to be synchronous on a global scale.